Immunocompetent mouse model of endometriosis.

6–8 weeks-old CD1 female mice were primed with PMSG for 48 hours. Uterine tissues were then harvested and minced into tiny cell aggregates after myometrial removal. Female mice with the same genetic background were subjected to ovariectomy and served as recipients. 2 weeks after surgery, equal volumes of uterine cell aggregate suspension were transferred into the peritoneal cavities of recipients. Endometriosis was maintained by subcutaneous administration of 100 ng of E2 once every 4 days until tissue collection. For the studies of the role of P4 in endometriosis, 1 mg of P4 (pre-P4) was administrated along with E2 beginning at 4 days before transplantation. For P4-resistance experiments (Post-P4), 1 mg of P4 was administration along with E2 beginning at 4 days after transplantation. The ectopic lesions were assessed under a dissecting microscope at different days after endometrial cell transplantation (n = 6 per treatment group).